The invention relates to a device for coupling attachment chucking jaws to basic jaws which are adjustably guided in the chuck body of a chuck and which are connectable in form-closing manner by a radial motion to the attachment chucking jaws. Each basic jaw has an extension which projects in the axial direction of the chuck body and on which is disposed a stop surface as well as a projection in the form of a locking nose projecting inwardly and/or outwardly perpendicular to the axis. A recess of the extension is machined into each attachment chucking jaw. Each attachment jaw is in the chuck body and secured against rotation. Each recess is provided with a countersurface interacting with the stop surface of the extension and there is inserted in each basic jaw for the arresting of the attachment chucking jaws, an axially movable locking member which can be locked in a recess machined in the attachment jaws.
An attachment chucking jaw change system of this kind is known from German OS No. 33 37 047 (U.S. patent application No. 657,339 now U.S. Pat. No. 4,634,207, and has also proven successful in practical application. The locking members provided therein for the arresting of the attachment chucking jaws in their coupled position are designed as detent bolts which are movably inserted against the force of a spring in the extension of a basic jaw and engage associated recesses in the attachment chucking jaws. By means of tools which can be applied through these recesses and are held in a pallet, the detent bolts an be pushed back for a change of attachment chucking jaws, thus releasing the lock in short order. It has, however, proven to be a disadvantage that the attachment chucking jaws must have a hole which cannot be closed and can be contaminated by dirt. This can lead to operating breakdowns because the contact between attachment chucking jaws and basic jaws can be impaired and the detent bolts sometimes get caught on acount of chips or other dirt particles. Monitoring the respective operating status, therefore, is associated with considerable expense in this device.
In addition, axial forces to push back the springs acting upon the detent bolts must be transmitted through the pallet or a handling device for carrying the attachment chucking jaws, a requirement which often ircreases the structural costs. Moreover, the springs assigned to the basic jaws or to the attachment chucking jaws can break, in which case an automatic, reliable detention and, hence, locking of the attachment chucking jaws is no longer assured so that there is no guarantee in this case that a workpiece is reliably chucked.